This invention relates to noise control for an earthmoving vehicle and more particularly to a noise silencer provided forwardly of the radiator and removably attached to an engine enclosure.
In general, an enclosure for an engine compartment in an earthmoving vehicle consists of a hood, enclosures (side covers), dash board, radiator guard and an under guard. The enclosure protects the engine and its accessories from damage due to pebbles, branches of trees, and the like as well as shields noise emanating from the engine.
Recently the noise control for earthmoving vehicles has come to the forefront and a demand for a countermeasure to reduce the noise has arisen. As a result, strict limitations or regulations have been imposed on the earthmoving vehicles such as for instance the noise levels of vehicles which should be less than 65 db (A) as measured at a point 30 m apart from a vehicle in its nonmovable condition and less than 75 db (A) as measured at a point 30 m apart from a vehicle in its operating condition.
Prior art references having noise control apparatuses are U.S. Pat. No. 3,812,927 and Japanese Laid-open Utility Model SH051-3733. The former discloses a radiator in which a radiator mask in front of the radiator is of such shape that noise from the engine is guided upwardly through a top opening with sound absorbing material being bonded to the inner surfaces of the mask. The latter discloses a radiator in which there is provided an opening in the front portion of a radiator with the aforesaid opening being covered with ducts having a sound absorbing material bonded to the inner surfaces of the ducts. The above both attempts are successful as a noise control means to some extent. However, the radiator mask (the former attempt) and the ducts (the latter attempt) can not be removed as required and, in addition, the opening is directed only upwards with the result that foreign matter such as pebbles, sand, soil, rain, water and the like pollute or damage the sound absorbing materials provided inside and in some cases such foreign matter enters the engine compartment.
Japanese Laid-open Utility Model Publication SH052-105 improves the aforesaid shortcomings by providing upper and lower openings for a radiator mask. However, the aforesaid openings are large in diameter so that air being blown from the fan through the lower opening impinges on the ground and thus blows dust and sand upwardly causing discomfort for the operator.